jp7 Posted December 14, 2003 Share Posted December 14, 2003 Hi All, now winters approaching i thought i'd get to the bottom of a problem with my brakes. They are standard dedion discs all round with greenstuff pads. All fine on the road but its on trackdays that i have a problem. Alls fine for the first couple of sessions, then when venturing back on the circuit again, there's very little braking at all 😳 until i 'pump up' the pedal again, then they seem ok again. I leave it in gear between sessions with the handbrake off. I change the fluid every year and bleed before each trackday. I noticed that the rears are getting very hot in comparison to the front. So whats causing this? Is this brake fade? How do i cure it? Would cross-drilled rear discs have any effect, or what about fitting 'redstuff' pads at the back as i believe they work better at highter temperatures, with a lower friction coeff. so as not to alter the balence. Would a race master cylinder have any effect? Cheers Andy Link to comment Share on other sites More sharing options...
rgrigsby Posted December 14, 2003 Share Posted December 14, 2003 It's ye olde Caterham rear brakes overheating problem... there are lots of solutions ranging from vents to the rear brakes, different pads, vented disks but the easiest by far is to switch to a better brake fluid such as AP600 or Castol SRF AP600 is a relatively cheap solution that works fine on my car with slicks during races. Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
jp7 Posted December 14, 2003 Author Share Posted December 14, 2003 Hi Rob, i'd been using Halfords Dot5.1. Are the fluids you suggest compatable with a system thats had 5.1 in it. Am i right in thinking you cant mix a synthetic with a mineral? cheers Andy Link to comment Share on other sites More sharing options...
rgrigsby Posted December 14, 2003 Share Posted December 14, 2003 Yup you can't mix the two, I can't remeber whether 5.1 is synthetic or not? Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
Asklepios Posted December 14, 2003 Share Posted December 14, 2003 Andy, Before puting expensive brake fluids to the test I would encourage you to thoroughly bleed the present system. I really should say exchange with fresh ,and then bleed. Link to comment Share on other sites More sharing options...
Rob Walker Posted December 14, 2003 Share Posted December 14, 2003 You are thinking the wrong way round. With the standard brake set up the rears overbrake the fronts and are also the worst design having a flat single piston surface that efficiently transmitts the heat into the fluid, to compound this the rears are poorly ventilated. I would put some quality pads up front with a high coefficient of friction these will then restore proper brake balance if standard pads are used in the rear. Flush out the system and refill with high spec fluid. Fitting the uprated master cylinder will only mask your problem. Link to comment Share on other sites More sharing options...
jp7 Posted December 14, 2003 Author Share Posted December 14, 2003 Hi All, thanks for the replies. Rob, what pads are we taking here, have you any suggestions? I have greenstuff allround, the rear wheels get really black with dust, which would suggest that they are overheating. Do they need changing as well? cheers Andy Link to comment Share on other sites More sharing options...
rgrigsby Posted December 14, 2003 Share Posted December 14, 2003 If they are getting dusty then they are definetly overheating.... have you got standard fronts? Pagid RS14 rears work well but you will need something similar up front as well, I'm not 100% sure what the best option is. Oh and the Pagid's aren't cheap and have a tendency to squeak a bit!! if you're in kent I have a spare set I used to use (since upgraded the brakes) you could borrow to try out. You will need to change the fronts at the same time though Rob G www.SpeedySeven.com Link to comment Share on other sites More sharing options...
Rob Walker Posted December 15, 2003 Share Posted December 15, 2003 Andy, I would use the standard Caterham rear pads, Pagid RS14 or if you are on a budget Pagid Blues on the front and fill with Castrol SRF. Link to comment Share on other sites More sharing options...
jp7 Posted December 15, 2003 Author Share Posted December 15, 2003 Thanks for the replies. I put EBC greenstuff in the back thinking they would be better than the standard caterham pad, but i've still got the caterham pads so i'll change them back. Is castrol SRF synthetic? If i was to go down the upgrade route for the front, caterham or james whitings Alcons, would this help to prevent the problem? I'm in the process of tuning the engine to slr spec and had considered upgrading anyway. Any thoughts. cheers Andy Link to comment Share on other sites More sharing options...
Rob Walker Posted December 15, 2003 Share Posted December 15, 2003 The uprated fronts will take a lot of the load off the rear brakes and will improve your braking by also giving you better balance. Trying a set of good pads up front and some high spec fluid may be all you need, don`t forget that the roadsports race with standard brakes. Its all too easy to just go on the upgrade route but that can lead to more problems. Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted December 15, 2003 Share Posted December 15, 2003 Hi Andy, I'd chuck the Green stuff pads in the bin (I recently threw out a brand new set of rears because I would not put them on my car and my concience wouldn't let me sell them to fellow 7 owner). Alot of people have got on well with them but I found they went dead after a few heat cycles and worst of all, only lasted 3 trackdays (if you used your brakes properly! ). Also their claim about being dust free is a bit misleading. I do stress that this was my finding and I know it doesn't concur with what alot of other people have found. The red stuff was much better but still didn't had the problem of loosing feel after a few heat cycles. It sounds like your problem is water in the fluid allowing it to boil and aerate when heated. I'd go for a fluid change myself. SRF is a Dot 4 compliant synthetic fluid. It's very expensive, as are Pagid RS14's. I use both of these but I suspect a cheaper and probably nearly as good solution would be AP600 with good old Mintex 1144's. Having said that, I love my RS14's. Although they are very expensive, I suspect with their longevity they will work out cheaper than Green Stuff pads! Alex Link to comment Share on other sites More sharing options...
jp7 Posted December 16, 2003 Author Share Posted December 16, 2003 Hi Alex, i've noticed a few bubbles coming out of the rear drivers side caliper when it was bled. Whats 'very expensive' as regards to the fluid and the pads? Does the srf fluid need to be changed every year? cheers Andy Link to comment Share on other sites More sharing options...
stevefoster Posted December 16, 2003 Share Posted December 16, 2003 SRF and AP600 are pretty similar in properties. Both around 300 deg C boiling and both pretty hygroscopic. You need to change the fluid about twice a year to keep the brake in top condition. AP600 is cheaper and for me available locally. I had exactly the same probs you describe. Big brakes front and standard rear. 9" slicks on the rear meant I could run Pagid RS14 rears and get good braking effect. Never a problem on track but the heat soak from being in the pits overheats the rears... what of the boggo seals after this type of punishment. So far so good though! AP600 may hide the symptom but those rears are getting mighy hot. I tried vents and they work on track but not against the heat soak! I am looking at moving the calliper to a more sensible 3 or 9 o'clock position to hopefully solved the problem. When was the last time you saw a brake calliper at 12 o'clock on the disk...Never ever. Not on anything mildly sporty or race oriented.... Design fault, engineering mistake etc. Hants (North) and Berkshire Area club site here My racing info site here Edited by - stevefoster on 16 Dec 2003 16:16:34 Link to comment Share on other sites More sharing options...
jp7 Posted December 16, 2003 Author Share Posted December 16, 2003 So let me get this right. The Castrol SRF fluid is Dot4 compliant, so does that mean it can be bled straight into my car and no adverse effects will come from a bit of mixing with the Halfords Dot 5.1(non synthetic) thats pushed out. ie. they're compatable. Is that the same for AP600. I only run my car from April to October so changing every 6 months isnt really an issue. What pads should i be using on the back?, standard caterham offering, and what about up front? mintex M1144 or Pagid RS14's. Steve, where do you buy the AP600 from and how much, i'm in Lightwater, Surrey. I see in demon thieves thats its about 9.80+vat and the SRF is 38+vat 😳 cheers Andy Link to comment Share on other sites More sharing options...
heavenly7 Posted December 16, 2003 Share Posted December 16, 2003 Just been throught the braking issue myself. Performance brakes were recommended on another thread and sell Pagids. The fellow there (sorry cant remember his name) is a genius! He will tell you that in fact Castrol SRF has a significantly higher boiling point than even AP600 - 330 dc I think, and is therefore the ultimate brake fluid. Whether it is justified in a Caterham I think is doubtful. People talk about how hydroscopic these fluids are by I was interested to learn that their boiling points at the DOT 4 test standard after absorbing water is still significantly higher than standard DOT4 fluids before they have absorbed any water. I have just replaced the brakes with the ceramic Pagids all round. Performance sell their own branded fluid which has a very similiar performance to AP600. The improvement is amazing and no squeaks at all. We werent sure how much fluid was need to completely flush the system but 1 litre did the job so if you want to go for SRF one bottle will do the job (only comes in litre bottles apparently). Link to comment Share on other sites More sharing options...
Alex Wong1697456877 Posted December 16, 2003 Share Posted December 16, 2003 Andy, About £250 should get you a complete set of Pagids and some decent fluid. I had standard Dot4 fluid in mine and flushed it out with SRF, then filled it up with SRF. Not sure about Dot 5.1 and changing to Dot 4. Anybody else know? I'd personally go start with AP600 and Mintex 1144's all round and see how you get on (provided you can change from DOT 5.1 to AP600). I doubt there is much benefit in SRF over AP600 although as I started with SRF and it works for me, I haven't tried changing to anything else. The worries about cold braking with race pads have never been a problem for me although the RS14's are very good in this respect - much better than say EBC reds. Give DaveK a call at Demon Tweeks for Mintex's and fluid. If you want to try Pagids, Fluke Motorsport quote the following prices : Caterham std rear E1163 - RS4-2 £88.55 Caterham std rear E1163 - RS14 £98.61 Caterham std front E3102 - RS4-2 £104.64 Caterham std front E3102 - RS4-4 £104.64 Caterham std front E3102 - RS14 £114.71 Caterham std front E3102 - RS15 £118.15 AP upgrade front E1265 - RS4-2 £112.69 AP upgrade front E1265 - RS4-4 £112.69 AP upgrade front E1265 - RS4-2-1 £112.69 AP upgrade front E1265 - RS14 £122.76 AP upgrade front E1265 - RS19 £140.87 AP upgrade rear E1363 - RS4-2 £88.55 AP upgrade rear E1363 - RS14 £98.61 See http://www.fluke-motorsport.co.uk/products/braking/index.html Alex Edited by - Alex Wong on 17 Dec 2003 00:07:57 Link to comment Share on other sites More sharing options...
stevefoster Posted December 16, 2003 Share Posted December 16, 2003 AP600 is the same: compatible after a good flushing with AP600. If you don't flush well then crystals can apparently form. I buy it from Autocross was in Binfield might have moved to Wokingham by now. Last bought for £11.50 for 500ml inc VAT. Just checked. The orignial partners have split Mr Cross and co are still in Binfield and I guess still sell the same sort of stuff. I have found them useful for roll bar padding, exhaust packing material, fuel pipe and unions, brake connector / aeroquip, wheel studs and nut and brake fluid. See http://www.xsportracing.com/ Hants (North) and Berkshire Area club site here My racing info site here Edited by - stevefoster on 16 Dec 2003 23:59:50 Link to comment Share on other sites More sharing options...
jp7 Posted December 17, 2003 Author Share Posted December 17, 2003 Thanks everyone for all the posts. If i go for Pagid RS14's on the front, would it be ok to put them on the back as well, bearing in mind i have the standard brakes all round, or would i be better off with just the standard caterhm pad. Also, my rear discs are a little grooved/worn, is it best to replace these at the same time. If i'm doing that is there any benefit to fitting drilled/spiral grooved types. cheers Andy Link to comment Share on other sites More sharing options...
Rob Walker Posted December 17, 2003 Share Posted December 17, 2003 Heh Andy why not read what has been post to you? The whole idea has been to redress the brake bias from that off being too much to the rear. If you put the RS14 on the rears you will still ahe the same problem, only worse as much more heat will be generated and transmitted into the rear calipers. If you have money to burn and you want the correct engineering solution then go ahead and fit the RS14 pads all round and also fit an adjustable brake bias valve into the rear circuit. You can then reduce the effect of the rear brakes and the amount of heat that they will generate. Link to comment Share on other sites More sharing options...
jp7 Posted December 17, 2003 Author Share Posted December 17, 2003 Yep, fair point , i got a bit confused by Alex's comment about fitting the pads all round. I've re-read it all and your right. Andy Edited by - ANDY PERRY on 17 Dec 2003 19:43:37 Edited by - ANDY PERRY on 17 Dec 2003 19:44:57 Link to comment Share on other sites More sharing options...
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